Roman Numeral Converter
Convert numbers to Roman numerals and back, both ways.
About the Roman Numeral Converter
This Roman Numeral Converter works in both directions: type a number from 1 to 3999 to get its Roman numeral, or type a Roman numeral to get the number back. It validates what you enter, so it will tell you when a Roman numeral is not written in the correct, canonical form (for example 'IIII' instead of 'IV'). Handy for dates, clock faces, book chapters, movie sequels and copyright years. Everything is computed in your browser.
How to use it
- Enter a whole number between 1 and 3999 in the left field to see its Roman numeral.
- Or type a Roman numeral in the right field to convert it back to a number.
- Watch the other field update automatically as you type.
Frequently asked questions
Why is the limit 3999?
Standard Roman numerals only go up to 3999 (MMMCMXCIX). Larger numbers need a bar notation that is rarely used today, so this tool sticks to the standard range.
Why does it reject some Roman numerals?
It checks that the numeral is written in proper subtractive form. 'IV' is valid but 'IIII' is not, so invalid spellings are flagged rather than silently converted.
Is anything sent to a server?
No. The conversion runs entirely in your browser.
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